Chemical mechanical polishing apparatus and method of manufacturing semiconductor device

ABSTRACT

A chemical mechanical polishing apparatus includes a polishing head, including a polishing head body, a membrane attached to a lower portion of the polishing head body, and a reflector disposed between the polishing head body and the membrane, a platen including an opening, an emitter disposed below the opening of the platen, the emitter configured to emit terahertz waves, a detector disposed below the opening of the platen, the detector configured to receive the terahertz waves emitted by the emitter and reflected by the reflector, and an analyzer configured to analyze an electrical signal generated by converting the terahertz waves received by the detector, the analyzer configured to determine a polishing end point.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application claims priority under 35 USC § 119 to Korean Patent Application No. 10-2018-0103315 filed on Aug. 31, 2018 in the Korean Intellectual Property Office, the disclosure of which is hereby incorporated by reference in its entirety.

BACKGROUND 1. Field

The present inventive concept relates to a chemical mechanical polishing apparatus and a method of manufacturing a semiconductor device.

2. Description of Related Art

A chemical mechanical polishing (CMP) process is a process for planarization of a surface of a substrate by combining a mechanical polishing effect using an abrasive with a chemical reaction effect using an acid or a base solution.

The CMP process, described above, is used for planarization of an insulating material used in a layer such as shallow trench isolation (STI) or interlayer dielectric (ILD), or for planarization of a layer including a metal such as a tungsten plug and copper wiring, or the like.

SUMMARY

An aspect of the present inventive concept is to provide a CMP apparatus capable of detecting an accurate polishing end point in a CMP process.

According to an example embodiment of the present inventive concept, a chemical mechanical polishing apparatus includes: a polishing head, including a polishing head body, a membrane attached to a lower portion of the polishing head body, and a reflector disposed between the polishing head body and the membrane, a platen including an opening, an emitter disposed below the opening of the platen, the emitter configured to emit terahertz waves, a detector disposed below the opening of the platen, the detector configured to receive the terahertz waves emitted by the emitter and reflected by the reflector, and an analyzer configured to analyze an electrical signal generated by converting the terahertz waves received by the detector, the analyzer configured to determine a polishing end point.

According to an example embodiment of the present inventive concept, a chemical mechanical polishing apparatus includes: a platen including an opening, a polishing head disposed on the platen and configured to support a substrate, an emitter disposed below the opening, the emitter configured to irradiate the substrate with the terahertz waves, and a detector disposed adjacent to the emitter, the detector configured to receive the terahertz waves passing through the substrate, wherein the polishing head includes a reflector configured to reflect the terahertz waves passing through the substrate.

According to an example embodiment of the present inventive concept, a chemical mechanical polishing apparatus includes: a polishing head including a reflector, the polishing head configured to support a substrate, an emitter disposed below the polishing head, the emitter configured to irradiate the substrate with terahertz waves, and a detector disposed adjacent to the emitter, the detector configured to receive the terahertz waves passing through the substrate and then reflected by the reflector.

BRIEF DESCRIPTION OF DRAWINGS

The above and other aspects, features and other advantages of the present disclosure will be more clearly understood from the following detailed description, taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a schematic plan view illustrating a chemical mechanical polishing apparatus according to an example embodiment;

FIG. 2 is a side view illustrating a chemical mechanical polishing apparatus according to an example embodiment;

FIG. 3 is a cross-sectional view illustrating a portion of a polishing head according to an example embodiment;

FIG. 4 is a view illustrating a reflector according to an example embodiment;

FIG. 5 illustrates an in-situ thickness monitoring process during a polishing process in a chemical mechanical polishing apparatus according to an example embodiment;

FIG. 6 illustrates points of a substrate, in which in-situ thickness monitoring is performed during one revolution of a platen during a polishing process;

FIG. 7 illustrates a reference time domain waveform and a measured time domain waveform;

FIG. 8 is a flow diagram in which a polishing end point is determined in a chemical mechanical polishing apparatus according to an example embodiment; and

FIG. 9 is a view illustrating a reflector according to an example embodiment.

DETAILED DESCRIPTION

Hereinafter, example embodiments of the present disclosure will be described with reference to the accompanying drawings.

FIG. 1 is a schematic view illustrating a chemical mechanical polishing apparatus according to an example embodiment.

Referring to FIG. 1, a chemical mechanical polishing apparatus 10 may include platens 20, polishing heads 30, slurry supply units 40, and conditioners 50. The chemical mechanical polishing apparatus 10 may further include a multi-head carousel 36, an exchanger 15, a loading/unloading unit 17, and a robot R.

The platens 20 may include a window 26. A polishing pad may be mounted on the platens 20. The polishing pad may be disposed not to cover the window 26. A polishing process may be sequentially performed to substrates disposed on the platens 20, or may only be performed to substrates disposed on some platens 20. The window 26 allows terahertz waves to pass therethrough. As described later, an emitter emitting terahertz waves and a detector receiving terahertz waves may be mounted below the window 26.

A slurry supply unit 40, supplying slurry to the polishing pad, may be disposed on one side of the platen 20.

The polishing heads 30 may be attached to the multi-head carousel 36 to be rotated, and may move to the platens 20 and the loading/unloading unit 17. For example, the polishing heads 30 may be configured to respectively face the platens 20 and the loading/unloading unit 17. For example, the polishing heads 30 may rotate about the center of the multi-head carousel 36 to sequentially face the platens 20 and the loading/unloading unit 17. The polishing heads 30 may be configured such that a lifting operation and a rotating operation may be performed independently of each other. The exchanger 15 may transfer a substrate, on which polishing is to be performed, to the loading/unloading unit 17, or may export a substrate, on which polishing is performed, from the loading/unloading unit 17. The robot R may export the substrate to be polished from the cassette and transfer the substrate to the exchanger 15, or may carry the substrate, in which polishing is finished, out of the exchanger 15 and may carry the substrate into the cassette.

The conditioner 50 may adjust a state of the polishing pad to maintain a constant polishing rate.

FIG. 2 is a side view illustrating a chemical mechanical polishing apparatus according to an example embodiment.

Referring to FIG. 2, the platen 20, in which the polishing pad 21 is mounted on a surface, may be connected to a first rotating shaft 22 and may be rotated. For example, the platen 20 may be configured to rotate via the first rotating shaft 22. The polishing head 30, supporting a substrate W to which a CMP process is applied, may be disposed on the polishing pad 21. The polishing head 30 may be connected to a second rotating shaft 32 and may rotate. Slurry S may be supplied to one region of the polishing pad 21 from the slurry supply unit 40. The slurry S is supplied to the polishing pad 21, which rotates, and then the polishing head 30 rotates in a state in which the polishing head 30 is lowered to allow the substrate W to be in close contact with the polishing pad 21. Thus, a polishing target film formed on the substrate W may be polished by the slurry S. The polishing target film may be an insulating film for formation of a shallow trench isolation (STI) or an interlayer dielectric (ILD) film covering gate patterns or metal wirings.

The polishing head 30 may include a polishing head body 31 coupled to the second rotating shaft 32, a membrane 44 attached to a lower portion of the polishing head body 31, and a reflector 42 disposed between the polishing head body 31 and the membrane 44. The membrane 44 may support the substrate W by a suction force. The membrane 44 and the reflector 42 will be described in more detail below with reference to FIGS. 3 and 4.

The platen 20 may include a hole or opening in which the window 26 is mounted. Below the window 26 of the platen 20, an emitter 61, irradiating terahertz waves to the substrate W, and a detector 64, receiving the terahertz waves passing through the substrate W, may be disposed adjacent to each other. The terahertz waves refer to electromagnetic waves having a wavelength of 3 mm to 30 μm. The emitter 61 may include a photoconductive antenna element using femtosecond laser as an excitation light source. The detector 64 may be a device that is configured to detect the terahertz waves, e.g., to detect an intensity of the terahertz waves. For example, the detector 64 may include an antenna or a similar component to an antenna. For example, the detector 64 may include a conductor part or a photosensitive part to sense the terahertz waves. For example, the detector 64 may include a nanowire having a sub micrometer diameter on a semiconductor substrate. For example, the nanowire may include a gold nanowire, and the semiconductor substrate may include a GaAs substrate. In certain embodiments, the detector 64 may include an electronic device and/or a semiconductor device connected to a sensing part, e.g., the conductor part or the photosensitive part. The electronic/semiconductor device may electronically transmit the detected terahertz wave information to an analyzer described below.

The emitter 61 and the detector 64 are coupled to the platen 20 and may rotate with the platen 20. While a CMP process is performed, the emitter 61 may irradiate terahertz waves 62 having a pulse shape to the substrate W through the window 26. For example, the window 26 may be formed of glass, quartz, or another material which transmits the terahertz waves 62. For example, the window 26 may include an insulating material which transmits the terahertz waves 62. For example, the emitter 61 may be an electromagnetic wave emitter emitting terahertz electromagnetic waves, e.g., terahertz radiation. The detector 64 may receive the terahertz waves 63, passing through the substrate W and then reflected by the reflector 42, through the window 26. The detector 64 may convert the received terahertz waves 63 into an electrical signal having a waveform over time, e.g., an electrical signal with a time-domain waveform.

While a polishing process is performed, a change in thickness of a polishing target film on the substrate W may be monitored in-situ by the emitter 61 and the detector 64, coupled to the platen 20, and finally a polishing end point may be determined.

The emitter 61 and the detector 64 may be connected to an analyzer 71. The analyzer 71 may control an operation of the emitter 61, and may determine a polishing end point by analyzing the electrical signal having a waveform over time, transmitted by the detector 64, e.g., the electrical signal having a time-domain waveform.

The analyzer 71 is connected to a display device 73, and the display device 73 may provide information processed in the analyzer 71 to a user. For example, the analyzer 71 may be a general purpose computer or may be dedicated hardware or firmware associated hardware (e.g., application-specific hardware). For example, the analyzer 71 may be an electronic device including logic circuit and may be configured to be operated by software or firmware implemented in the analyzer 71. For example, the analyzer 71 may include a memory device and/or a processing device therein.

FIG. 3 is a cross-sectional view illustrating a portion of a polishing head according to an example embodiment. FIG. 4 is a view illustrating a reflector according to an example embodiment.

Referring to FIGS. 3 and 4, a polishing head 30 according to an example embodiment may include a membrane 44 disposed in a lower portion of the polishing head body 31 and supporting the substrate W, and a membrane clamp 46 to which the membrane 44 is fixed. The reflector 42 is coupled to the membrane clamp 46, and is disposed between the membrane clamp 46 and the membrane 44.

The membrane clamp 46 may include gas passages 34 a, 34 b, and 34 c. Through the gas passages 34 a, 34 b, and 34 c, air/gas may be pumped in or inhaled. The membrane 44 may be formed of a flexible material, for example, silicone. The membrane 44 may be divided into three regions in each of which internal pressure may be separately/independently adjusted/controlled from the others. During a CMP process, internal pressures of the three regions are appropriately adjusted, thereby increasing uniformity of a polishing process. According to a structure of the membrane 44, a lower surface of the membrane clamp 46 may include three regions in the form of rings, spaced apart from each other. As an example, the membrane 44 is illustrated to be divided into three regions corresponding to gas chambers respectively connected to gas passages 34 a, 34 b and 34 c in FIG. 3, but the number of regions in which internal pressure is able to be separately adjusted may be changed.

The reflector 42 may include three reflecting regions 42 a, 42 b, and 42 c in the form of rings, spaced apart from each other. The reflector 42 may include a support 42 s, and a metal layer 42 r coated on a surface of the support 42 s. The support 42 s may be in contact with a lower surface of the membrane clamp 46. The metal layer 42 r may be formed of gold (Au), silver (Ag), aluminum (Al) or a combination thereof. The metal layer 42 r may be formed of a single layer or a multilayer structure.

The reflecting regions 42 a, 42 b, and 42 c of the reflector 42 may have widths in the radial direction, respectively. A first reflecting region 42 a may have a first width W1, a second reflecting region 42 b may have second width W2, and a third reflecting region 42 c may have a third width W3. The first width W1, the second width W2, and the third width W3 may have the same value.

In an example embodiment, at least one among the first width W1, the second width W2, and the third width W3 may have a different value. For example, the second width W2 of the second reflecting region 42 b may be the widest. Alternatively, the first width W1 of the first reflecting region 42 a may be the widest, while the third width W3 of the third reflecting region 42 c may be the narrowest.

FIG. 5 illustrates an in-situ thickness monitoring process during a polishing process in a chemical mechanical polishing apparatus according to an example embodiment.

The terahertz waves 62, emitted by the emitter (61, see FIG. 2) may sequentially pass through the window 26 disposed in the hole 24 of the platen 20, the slurry S, the substrate W coated with a polishing target film TM, and the membrane 44, and may be then reflected by the metal layer 42 r of the reflector 42. The reflected terahertz waves 63 may sequentially pass again through the membrane 44, the substrate W, the slurry S, and the window 26, and may be received by the detector (64, see FIG. 2).

The detector 64 may convert the received terahertz waves 63 into an electrical signal having a waveform over time, e.g., an electrical signal having a time domain waveform.

FIG. 6 illustrates points of a substrate in which an in-situ thickness monitoring is performed during one revolution of a platen during a polishing process.

Referring to FIG. 6, thickness monitoring using terahertz waves may be performed in-situ at a plurality of measurement points of the substrate W during one revolution of the platen (20, see FIG. 2). An arrow in FIG. 6 indicates a rotation direction of the platen 20. In FIG. 6, eight points are illustrated by way of example, but the number of measurement points may be changed depending on variables such as a rotation speed of the platen 20, or the like. For each measurement point, a series of processes, described with reference to FIG. 5, may be performed.

FIG. 7 illustrates a reference signal and a measurement signal with a time domain waveform.

A maximum amplitude d2 at a measurement signal, measured while a polishing process is performed, is smaller than a maximum amplitude d1 at a reference signal, and a time delay value t2 of the maximum amplitude d2 at a measurement signal is greater than a target time delay value t1 of the maximum amplitude d1 at a reference signal. As a polishing process is continuously performed and thus a thickness of a polishing target film of the substrate W is reduced, a maximum amplitude d2 and a time delay value t2 at a measurement signal become close to a maximum amplitude d1 and a target time delay value t1 at a reference signal.

A point, at which a time delay value t2 at a measurement signal coincides with a target time delay value t1 at a reference signal, is a polishing end point.

FIG. 8 is a flow diagram illustrating a method for determining a polishing end point in a chemical mechanical polishing apparatus according to an example embodiment.

Referring to FIG. 8, a substrate having a polishing target film (for example, an insulating film) is mounted on a polishing head and is in close contact with the polishing pad, thereby starting a polishing process (S10).

Thickness measuring using terahertz waves with respect to the substrate W during one revolution of a platen is performed to obtain a measurement signal (S20). As described with reference to FIG. 6, measurement signals from a plurality of measurement points of the substrate W during one revolution of a platen are received by a detector. Here, the measurement signal may refer to an average value of measurement signals received from a plurality of measurement points. Alternatively, the measurement signal may refer to an average value of a portion of measurement signals received from a plurality of measurement points. Alternatively, the measurement signal may refer to a measurement signal obtained from each measurement point.

An analyzer may extract a time delay value with a maximum amplitude from a measurement signal transmitted by the detector (S30). Next, the analyzer may compare the extracted time delay value with a preset target time delay value (S40). The analyzer may determine whether the polishing end condition is satisfied (S50). For example, the analyzer may determine whether the time delay value of the measurement signal matches the target time delay value. When the time delay value of the measurement signal matches the target time delay value, a polishing end condition is satisfied. Thus, the polishing process is terminated (S60). However, when the time delay value of the measurement signal is greater than the target time delay value, the polishing process is continuously performed and operations S20, S30, S40, and S50 are performed. For example, the terahertz radiation emitted from the emitter 61 may be delayed by the polishing target film TM, and the delay may depend on the thickness of the polishing target film TM. Therefore, the delay of the terahertz radiation may be referenced in determining the remaining thickness of the polishing target film TM so that the polishing end point may be determined be comparing the delay of the reference and the delay of the terahertz wave of the measured signal. In certain embodiments, the maximum amplitude d1 of the reference signal and the maximum amplitude d2 of the measured signal may be used to determine polishing end point. For example, the polishing target film TM may absorb a portion of the terahertz wave emitted from the emitter 61, and the absorption amount may depend on the thickness of the polishing target film TM so that the polishing end point may be determined be comparing the intensities of the reference and the measured terahertz wave signals, e.g., at their maximum amplitudes d1 and d2.

FIG. 9 is a view illustrating a reflector according to an example embodiment.

Referring to FIG. 9, a reflector 42′ may include two reflecting regions 42 a′ and 42 b′. A first reflecting region 42 a′ may have a first width W1′, while a second reflecting region 42 b′ may have a second width W2′. The first width W1′ may be greater than the second width W2′. In certain example embodiments, the second width W2′ may be greater than the first width W1′.

According to a structure of the reflector 42′, structures of a membrane 44 and a membrane clamp 46 may be changed correspondingly.

As set forth above, according to example embodiments of the present inventive concept, an accurate polishing end point may be detected in a CMP process using terahertz waves.

According to an embodiment of the present disclosure, a method of manufacturing a semiconductor device may include a CMP process described above.

For example, an insulation layer or a conductive layer may be formed on a substrate W. The substrate W may be loaded on a platen 20 of a chemical mechanical polishing apparatus 10 described above, and then, a CMP process may be performed on the substrate W. A pattern may be formed on the substrate W before the insulation layer or the conductive layer is formed on the substrate W, and the insulation layer or conductive layer may be planarized using the CMP process, for example, to form a corresponding pattern from the remaining portion of the insulation layer or conductive layer. After the CMP process is performed on the substrate W, additional patterning processes forming wirings and/or insulator patterns may be performed on the substrate W. After forming all predetermined patterns and/or layers on the substrate W, the substrate W may be diced into chips, and the chips may be packaged.

While example embodiments have been shown and described above, it will be apparent to those skilled in the art that modifications and variations could be made without departing from the scope of the present disclosure, as defined by the appended claims. 

What is claimed is:
 1. A chemical mechanical polishing apparatus, comprising: a polishing head, including a polishing head body, a membrane attached to a lower portion of the polishing head body, and a reflector disposed between the polishing head body and the membrane; a platen including an opening; an emitter disposed below the opening of the platen, the emitter configured to emit terahertz waves; a detector disposed below the opening of the platen, the detector configured to receive the terahertz waves emitted by the emitter and reflected from the reflector; and an analyzer configured to analyze an electrical signal generated by converting the terahertz waves received by the detector, the analyzer configured to determine a polishing end point.
 2. The chemical mechanical polishing apparatus of claim 1, wherein the reflector includes a plurality of reflecting regions in the form of rings.
 3. The chemical mechanical polishing apparatus of claim 2, wherein the plurality of reflecting regions are spaced apart from each other.
 4. The chemical mechanical polishing apparatus of claim 2, wherein the plurality of reflecting regions have the same width in a radial direction.
 5. The chemical mechanical polishing apparatus of claim 2, wherein one region of the plurality of reflecting regions has a first width in a radial direction, another region of the plurality of reflecting regions has a second width in the radial direction, and the first and second widths are different from each other.
 6. The chemical mechanical polishing apparatus of claim 2, wherein the polishing head further includes a membrane clamp disposed in a lower portion of the polishing head body and to which the membrane is fixed, and wherein the reflector is coupled to the membrane clamp, and is disposed between the membrane clamp and the membrane.
 7. The chemical mechanical polishing apparatus of claim 6, wherein the reflector includes a support and a metal layer coated on a surface of the support, and the support is in contact with the membrane clamp.
 8. The chemical mechanical polishing apparatus of claim 7, wherein the metal layer comprises gold, silver, aluminum, or a combination thereof.
 9. The chemical mechanical polishing apparatus of claim 1, wherein the detector is configured to convert the terahertz waves, passing through a substrate being polished and then reflected by the reflector, into an electrical signal having a time domain waveform, and wherein the analyzer is configured to compare a time delay value having a maximum amplitude of the electrical signal, transmitted by the detector, with a preset target time delay value, to determine the polishing end point.
 10. The chemical mechanical polishing apparatus of claim 1, wherein the emitter and the detector are coupled to the platen and are configured to rotate together with the platen.
 11. A chemical mechanical polishing apparatus, comprising: a platen including an opening; a polishing head disposed on the platen and configured to support a substrate; an emitter disposed below the opening, the emitter configured to irradiate the substrate with terahertz waves; and a detector disposed adjacent to the emitter, the detector configured to receive the terahertz waves passing through the substrate, wherein the polishing head includes a reflector configured to reflect the terahertz waves passing through the substrate.
 12. The chemical mechanical polishing apparatus of claim 11, wherein the reflector includes a plurality of reflecting regions in the form of rings, the plurality of reflecting regions spaced apart from each other.
 13. The chemical mechanical polishing apparatus of claim 11, wherein the polishing head further includes a membrane configured to support the substrate and a membrane clamp to which the membrane is fixed, and the reflector is coupled to the membrane clamp, and is disposed between the membrane clamp and the membrane.
 14. The chemical mechanical polishing apparatus of claim 13, wherein the reflector includes a support coupled to the membrane clamp and a metal layer coated on the support, and the metal layer comprises gold, silver, aluminum, or a combination thereof.
 15. The chemical mechanical polishing apparatus of claim 13, wherein a lower surface of the membrane clamp includes a plurality of regions in the form of rings, spaced apart from each other.
 16. The chemical mechanical polishing apparatus of claim 11, further comprising an analyzer configured to analyze the terahertz waves received by the detector, the analyzer configured to determine a polishing end point.
 17. A chemical mechanical polishing apparatus, comprising: a polishing head including a reflector, the polishing head configured to support a substrate; an emitter disposed below the polishing head, the emitter configured to irradiate the substrate with terahertz waves; and a detector disposed adjacent to the emitter, the detector configured to receive the terahertz waves passing through the substrate and then reflected by the reflector.
 18. The chemical mechanical polishing apparatus of claim 17, wherein the reflector includes a plurality of reflecting regions in the form of rings spaced apart from each other.
 19. The chemical mechanical polishing apparatus of claim 17, wherein the reflector includes a metal layer comprising gold, silver, aluminum, or a combination thereof.
 20. The chemical mechanical polishing apparatus of claim 17, wherein the polishing head further includes a membrane configured to support the substrate and a membrane clamp to which the membrane is fixed, and wherein the reflector is coupled to the membrane clamp, and is disposed between the membrane clamp and the membrane. 